I. Field
The following description relates generally to wireless communications, and more particularly to methods and apparatuses for coding control information.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, etc.). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), High Speed Packet (HSPA, HSPA+), and others. Moreover, wireless communication systems can be designed to implement one or more standards, such as IS-95, CDMA2000, IS-856, W-CDMA, TD-SCDMA, and the like.
In designing a reliable wireless communication system, special attention must be given to particular data transmission parameters. For instance, in a densely deployed network, where the spectrum is reused by different sectors and the coverage areas of these sectors overlap, signals may collide frequently due to different transmitters simultaneously accessing the same spectrum, which causes significant interference. For example, consider a wireless system with a transmitter TX_A and a receiver RX_A. The transmitter TX_A may be a sector or a base station. The receiver RX_A may be a mobile station or a relay station (Alternately, the transmitter TX_A may be a mobile station and the receiver RX_A may be a base station). The transmitter TX_A typically transmits a combination of data channels and control channels to RX_A and other receivers. The control channels may include, but are not limited to, acknowledgement channels, power control channels, resource assignment channels. etc.
In some cases, the interference caused by TX_B may be very high, thereby degrading the signal-to-noise ratio at RX_A to a point where it is unable to receive its control channels from TX_A. Such high interference levels are common in wireless technologies where the deployments are unplanned. Examples could include femtocell deployments, WiFi deployments etc. The problem is especially acute in systems with “restricted association” where a receiver is not allowed to connect to the strongest RF link. For example, a WiFi user may not be able to connect to his/her neighbor's WiFi Access Point even if the signal strength from the neighbor's access point is significantly higher than that of his/her own access point.
A common strategy to deal with such high interference levels is interference avoidance. In this case, TX_A and TX_B may be instructed to transmit in different time or frequency slots so that TX_B no longer interferes with TX_A. However, if either of TX_A or TX_B is in an area such that the signal-to-noise ratio is poor, receiving control data that includes such interference avoidance information may itself be difficult. Accordingly, it would be desirable to have a method and apparatus for robustly encoding/decoding control data transmitted within a noisy wireless environment.
The above-described deficiencies of current wireless communication systems are merely intended to provide an overview of some of the problems of conventional systems, and are not intended to be exhaustive. Other problems with conventional systems and corresponding benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.